Did you create the ADO connection using the correct bitism of 32-bit or 64-bit?
If your application is built as target x86 then you need to use a 32-bit ADO connection, if it is x64 then it needs to be a 64-bit ADO connection.
ADO connections do not currently work in projects whose target is anyCPU.
For a test please create a brand new connection with a different name and see if that works.
Thanks.